Over the years, there has been developed a substantial body of patent and other literature directed to the formation and properties of poly(aryl ethers) (hereinafter called "PAE"). Some of the earliest work such as by Bonner, U.S. Pat. No. 3,065,205, involves the electrophilic aromatic substitution (viz. Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this calss to a much broader range of PAE's was achieved by Johnson et al., Journal of Polymer Science, A-1, Vol. 5, 1967, pp. 2415-2427; Johnson et al., U.S. Pat. Nos. 4,108,837 and 4,175,175. Johnson et al. show that a very broad range of PAE's can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAE's including a broad class of poly(aryl ether ketones), hereinafter called "PAEK's".
In recent years, there has developed a growing interest in PAEK's as evidenced by Dahl, U.S. Pat. No. 3,953,400; Dahl et al., U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca, U.S. Pat. No. 4,339,568; Attwood et al., Polymer, 1981, Vol. 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983, Vol. 24, August, pp. 953-958; Attwood et al., Polymer Preprints, 20, No. 1, April 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, Vol. 24, September, pp. 258-260. In PAEK under the trademark Victrex PEEK. As PAEK is the acronym of poly(aryl ether ketone), PEEK is the acronym of poly(ether ether ketone) in which the phenylene units in the structure are assumed.
Thus PAEK's are well known; they can be synthesized from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. Most of the PAEK's are cystalline and at sufficiently high molecular weights, they are tough, i.e., they exhibit high values (&gt;50 ft-lbs/in.sup.3) in the tensile impact test (ASTM D-1822). They have potential for a wide variety of uses, and their favorable properties class them with the best of the engineering polymers.
Some PAEK's may be produced by the Friedel-Crafts catalyzed reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether as described in, for example, U.S. Pat. No. 3,065,205. These processes are generally inexpensive processes; however, the polymers produced by these processes tend to be brittle and thermally unstable. In contrast, PAEK's made by nucleophilic aromatic substitution reactions are tough crystalline polymers. Nucleophilic aromatic substitution reactions for producing PAEK's are described in the following references:
Canadian Pat. No. 847,963 describes a process for preparing polyarylene polyethers. The process comprises contacting equimolar amounts of a dihydric phenol and a dihalobenzenoid compound and at least one mole of an alkali metal carbonate per mole of dihydric phenol. The dihydric phenol is in situ reacted with the alkali metal carbonate to form the alkali metal salt thereof and the formed salt reacts with the dihalobenzeoid compound tp form the polyarylene polyether in the usual fashion.
U.S. Pat. No. 4,176,222 describes the preparation of aromatic polyethers containing SO.sub.2 and/or CO linkages by a nucleophilic reaction utilizing a mixture of sodium carbonate or bicarbonate and a second alkali metal carbonate or bicarbonate. The alkali metal of the second alkali metal carbonate or bicarbonate has a higher atomic number than that of sodium. The second alkali metal carbonate or bicarbonate is used in amounts such that there are 0.001 to 0.2 gram atoms of the alkali metal of higher atomic number per gram atom of sodium. The process is stated to take place faster when the combination of sodium carbonate or bicarbonate and the second alkali metal carbonate or bicarbonate are used. Also, the products are stated to be of higher molecular weight using such a combination.
The patent describes in Example 17 that when the reaction is carried out using only sodium carbonate, a polymer is obtained having a reduced viscosity of 0.60 dl/g as measured in concentrated sulfuric acid at 25.degree. C. at a concentration of one gm/100 ml. However, it is stated in the patent that when the polymer was compression molded into a film, the film was brittle and dark grey in color. In Example 18 of the patent, the polymerization was carried out using potassium carbonate instead of sodium carbonate and a high molecular weight polymer was produced (reduced viscosity of 1.55 as measured in concentrated sulfuric acid at 25.degree. C. at a concentration of one gm/100 ml.). However, the polymer was stated to contain a quantity of gel and also, the reaction vessel had acquired a black coating. In Example 19 of the patent, a mixture of potassium carbonate and sodium carbonate was used. The patent stated that the polymer produced has a high reduced viscosity and a tough off-white film was formed from it. Also, no gel was present in the polymer and the reaction vessel had not become discolored.
U.S. Pat. No. 4,320,224 also describes the production of aromatic polyetherketones in the presence of an alkali metal carbonate or bicarbonate in an amount providing at least 2 gram atoms of alkali metal per mole of starting bisphenol. The patent states that the sole use of sodium carbonate and/or bicarbonate is excluded.
U.S. Pat. No. 3,941,748 describes the use of alkali metal fluoride for preparing polyarylethers. The process requires that sufficient fluoride be present so that the total fluoride available (including that from any fluoroaryl monomers) can be at least twice the number of phenol (--OH) groups. The examples show it to be, in general, a slow process.
Imai, et al., in Makromol Chem., 179, pp. 2989-2991, 1978 describe the preparation of polysulfones in dipolar aprotic solvents using at least 500 mole percent of potassium fluoride based on the bisphenol. The process uses relatively low temperatures (about 100 C) to avoid polymer degradation but requires very long reaction times (48-70 hours).
U.S. Pat. No. 4,169,178 refers to the British counterpart of U.S. Pat. No. 3,941,748, i.e., British Pat. No. 1,348,630. The patent states that the amount of alkali metal carbonate required may be reduced in the preparation of aromatic polyethers by employing fluorophenols or difluorobenzenoid compounds as part or all of the halogen containing reactants. The patent states that the process gives faster reactions and higher molecular weights and less colored polymers than a process using potassium fluoride in place of potassium carbonate.
German Patent Application No. 3,342,433 describes a process for the preparation of aromatic polyethers which uses a mixture of (a) a lithium and/or an alkaline earth metal carbonate; and (b) a sodium, potassium, ribidium, and/or a cesium carbonate. The patent application states that it was totally unexpected to discover that high molecular weight polymers can be prepared via the nucleophilic polycondensation, if one uses the combination of the essentially non-reactive carbonates selected from the group of lithium or alkaline earth metal carbonates, with small amounts, that are per se insufficient to perform a successful polymerization, of a carbonate selected from the group of sodium, potassium, rubidium, or cesium carbonates.
European Patent Application No. 182,648 discloses a process for the preparation of an aromatic polymer which comprises (a) effecting the condensation of at least one halophenol; or (b) effecting the condensation of a mixture of at least one bisphenol with at least one dihalo-benzenoid compound; or (c) effecting the condensation of (i) at least one halophenol and (ii) a mixture of at least one bisphenol with at least one dihalo-benzenoid compound, in the presence of at least a base and at least one copper compound, wherein the base is in stoichiometric excess relative to the phenolic groups in (a), (b), or (c), at least one of the compounds in (a), (b), or (c) being a compound containing a ketone group, and in the halophenol or the dihalo-benzenoid compound the, or each halogen atom being activated by an inert electron-withdrawing group in at least one of the positions ortho- or para- to the, or each, halogen atom. The patent application states that polymers of increased molecular weight, as indicated by inherent viscosity, may be obtained from chlorine or bromine-containing monomers or a polymer of the same molecular weight may be obtained using a shorter polymerization time. Alkali metal hydroxides, carbonates or bicarbonates are cited as useful bases.
U.S. Pat. No. 4,638,044 describes the use of sodium carbonate or bicarbonate and an alkali metal halide selected from potassium, rubidium, or cesium fluoride or chloride, or combinations thereof. This process represents a significant improvement over the prior art. It, however, still makes use of relatively high amounts of fluoride salts which are corrosive; moreover, the rates of polymerization are relatively low when compared to those of the instant invention.